1. Field of the Invention
The present invention relates to the field of reciprocating electromagnetic devices, and in particular to a solenoid driven electromagnetic fluid pump having a magnetic circuit including a Hall effect switch detecting the position of a reciprocating piston.
2. Description of the Prior Art
Reciprocating piston electromagnetic fluid pumps as disclosed in the patent to Parker, U.S. Pat. No. 2,994,792, and Wertheimer, U.S. Pat. No. 3,381,616, have obtained wide commercial acceptance, but in a highly competitive field, improvements are very important. The earlier models of these pumps, as represented by Parker include an electrical switch in circuit relationship with a solenoid which is either mechanically or magnetically actuated by the piston at the end of the pumping stroke. Closing the switch energizes the solenoid retracting the piston to its cocked position. When the piston reaches the cocked position, the switch opens, de-energizing the solenoid and the pumping stroke is carried out under the force of a compressed spring. Although these types of pumps function very satisfactorily and have reasonable operating life, the electrical switch is subject to failure and is determinative of the pumps operating life.
To increase the life of the pump, blocking oscillators were subsequently introduced such as taught by Wertheimer and by Brown in U.S. Pat. No. 3,629,674. Blocking oscillators eliminated the electrical switch and increased the operating life of the pump. Pumps with blocking oscillators however are more complex since they require a detection coil in addition to the solenoid coil. Further, the operating temperatures of the pump were limited to the operating temperature range of the blocking oscillator.
The present invention is a reciprocating piston electromagnetic pump in which the electrical switch is replaced by a Hall effect switch in a magnetic circuit.